In so-called "advanced hair colouring", sections of the hair are subjected to a colouring treatment (which term is here used to encompass "bleaching" in addition to "tinting") without treating the remainder of the head of hair. One such conventional process is that known as "foil highlighting" in which strips of aluminium foil detached from a roll of such foil are folded around the section of hair to be treated together with the treating materials in paste form. Foil highlighting is very widely employed but suffers from a number of disadvantages. The foil can be used once only. The pieces of foil for each highlighting need to be prepared in advance. There is a tendency for leakage to occur unless the treatment is carefully carried out by someone with experience. The progress of the treatment cannot be followed and since there is a range of response with different hair types to the treatment materials, to ensure the treatment is completed, the materials are left in contact with the sections of hair concerned for longer than might be necessary. Lengthy and repeated exposure of hair to the materials conventionally employed will eventually damage the structure of the hair. It would therefore be desirable to maintain contact between the materials and the individual sections of hair for the minimum time that was necessary.